class_docstr: **CNN / Daily Mail** 数据集的 **Loader** ，用于 **extractive summarization task** 任务。
  如果你使用了这个数据，请引用 https://arxiv.org/pdf/1506.03340.pdf
  
  读取的 :class:`~fastNLP.core.DataSet` 将具备以下的数据结构：
  
  .. csv-table::
     :header: "text", "summary", "label", "publication"
  
     "['I got new tires from them and... ','...']", "['The new tires...','...']", "[0, 1]", "cnndm"
     "['Don't waste your time.  We had two...','...']", "['Time is precious','...']", "[1]", "cnndm"
     "['...']", "['...']", "[]", "cnndm"
  
  :param fields:
code: def __init__(self, fields=None):
      fields = fields or {
          "text": None,
          "summary": None,
          "label": None,
          "publication": None,
      }
      super(ExtCNNDMLoader, self).__init__(fields=fields)
  
file_path: fastNLP/fastNLP/io/loader/summarization.py
imports: import os
  from typing import Union, Dict
  from ..data_bundle import DataBundle
  from ..utils import check_loader_paths
  from .json import JsonLoader
label_desc: Use image node_id 1 to create a new ExtCNNDMLoader object from inherited base classes: JsonLoader with example: obj = ExtCNNDMLoader(fields)